make+scripts: add lint check for Golang version

To make sure we use the same Golang version everywhere, we add a new
linter step with scripts copied from lnd.

Author: guggero

Makefile

@@ -18,6 +18,11 @@ COMMIT := $(shell git describe --abbrev=40 --dirty --tags)
 COMMIT_HASH := $(shell git rev-parse HEAD)
 PUBLIC_URL := 
 
+# GO_VERSION is the Go version used for the release build, docker files, and
+# GitHub Actions. This is the reference version for the project. All other Go
+# versions are checked against this version.
+GO_VERSION = 1.22.6
+
 LOOP_COMMIT := $(shell cat go.mod | \
 		grep $(LOOP_PKG) | \
 		head -n1 | \
@@ -238,7 +243,17 @@ fmt: $(GOIMPORTS_BIN)
 	@$(call print, "Formatting source.")
 	gofmt -l -w -s $(GOFILES_NOVENDOR)
 
-lint: docker-tools
+check-go-version-yaml:
+	@$(call print, "Checking for target Go version (v$(GO_VERSION)) in YAML files (*.yaml, *.yml)")
+	./scripts/check-go-version-yaml.sh $(GO_VERSION)
+
+check-go-version-dockerfile:
+	@$(call print, "Checking for target Go version (v$(GO_VERSION)) in Dockerfile files (*Dockerfile)")
+	./scripts/check-go-version-dockerfile.sh $(GO_VERSION)
+
+check-go-version: check-go-version-dockerfile check-go-version-yaml
+
+lint: check-go-version docker-tools
 	@$(call print, "Linting source.")
 	$(DOCKER_TOOLS) golangci-lint run -v $(LINT_WORKERS)
 

scripts/check-go-version-dockerfile.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+
+# Function to check if the Dockerfile contains only the specified Go version.
+check_go_version() {
+    local dockerfile="$1"
+    local required_go_version="$2"
+
+    # Use grep to find lines with 'FROM golang:'
+    local go_lines=$(grep -i '^FROM golang:' "$dockerfile")
+
+    # Check if all lines have the required Go version.
+    if [ -z "$go_lines" ]; then
+        # No Go version found in the file. Skip the check.
+        return
+    elif echo "$go_lines" | grep -q -v "$required_go_version"; then
+        echo "$go_lines"
+        echo "Error: $dockerfile does not use Go version $required_go_version exclusively."
+        exit 1
+    else
+        echo "$dockerfile is using Go version $required_go_version."
+    fi
+}
+
+# Check if the target Go version argument is provided.
+if [ $# -eq 0 ]; then
+    echo "Usage: $0 <target_go_version>"
+    exit 1
+fi
+
+target_go_version="$1"
+
+# File paths to be excluded from the check.
+exception_list=(
+    # Exclude the tools Dockerfile as otherwise the linter may need to be
+    # considered every time the Go version is updated.
+    "./tools/Dockerfile"
+)
+
+# is_exception checks if a file is in the exception list.
+is_exception() {
+    local file="$1"
+    for exception in "${exception_list[@]}"; do
+        if [ "$file" == "$exception" ]; then
+            return 0
+        fi
+    done
+    return 1
+}
+
+# Search for Dockerfiles in the current directory and its subdirectories.
+dockerfiles=$(find . -type f -name "*.Dockerfile" -o -name "Dockerfile")
+
+# Check each Dockerfile
+for file in $dockerfiles; do
+    # Skip the file if it is in the exception list.
+    if is_exception "$file"; then
+        echo "Skipping $file"
+        continue
+    fi
+
+    check_go_version "$file" "$target_go_version"
+done
+
+echo "All Dockerfiles pass the Go version check for Go version $target_go_version."

scripts/check-go-version-yaml.sh

@@ -0,0 +1,75 @@
+#!/bin/bash
+
+# Function to check if the YAML file contains the specified Go version after
+# field 'go:'.
+check_go_version_yaml() {
+    local yamlfile="$1"
+    local required_go_version="$2"
+
+    # Use grep to find lines with 'go:'. The grep exist status is ignored.
+    local go_lines=$(grep -i '^\s*go:\s*"[0-9]\+\.[0-9]\+\(\.[0-9]\+\)\?"' "$yamlfile" || true)
+
+    # Check if any lines specify the Go version.
+    if [ -n "$go_lines" ]; then
+        # Extract the Go version from the file's lines. Example matching strings:
+        # go: "1.21.0"
+        local extracted_go_version=$(echo "$go_lines" | sed -n 's/.*go: "\([^"]*\)".*/\1/p')
+
+        # Check if the extracted Go version matches the required version.
+        if [ "$extracted_go_version" != "$required_go_version" ]; then
+            echo "Error finding pattern 'go:': $yamlfile specifies Go version '$extracted_go_version', but required version is '$required_go_version'."
+            exit 1
+        else
+            echo "$yamlfile specifies Go version $required_go_version."
+        fi
+    fi
+}
+
+# Function to check if the YAML file contains the specified Go version after
+# environment variable 'GO_VERSION:'.
+check_go_version_env_variable() {
+    local yamlfile="$1"
+    local required_go_version="$2"
+
+    # Use grep to find lines with 'GO_VERSION:'. The grep exist status is
+    # ignored.
+    local go_lines=$(grep -i 'GO_VERSION:' "$yamlfile" || true)
+
+    # Check if any lines specify the Go version.
+    if [ -n "$go_lines" ]; then
+        # Extract the Go version from the file's lines. Example matching strings:
+        # GO_VERSION: "1.21.0"
+        # GO_VERSION: '1.21.0'
+        # GO_VERSION: 1.21.0
+        # GO_VERSION:1.21.0
+        #   GO_VERSION:1.21.0
+        local extracted_go_version=$(echo "$go_lines" | sed -n 's/.*GO_VERSION[: ]*["'\'']*\([0-9.]*\).*/\1/p')
+
+        # Check if the extracted Go version matches the required version.
+        if [ "$extracted_go_version" != "$required_go_version" ]; then
+            echo "Error finding pattern 'GO_VERSION:': $yamlfile specifies Go version '$extracted_go_version', but required version is '$required_go_version'."
+            exit 1
+        else
+            echo "$yamlfile specifies Go version $required_go_version."
+        fi
+    fi
+}
+
+# Check if the target Go version argument is provided.
+if [ $# -eq 0 ]; then
+    echo "Usage: $0 <target_go_version>"
+    exit 1
+fi
+
+target_go_version="$1"
+
+# Search for YAML files in the current directory and its subdirectories.
+yaml_files=$(find . -type f \( -name "*.yaml" -o -name "*.yml" \))
+
+# Check each YAML file.
+for file in $yaml_files; do
+    check_go_version_yaml "$file" "$target_go_version"
+    check_go_version_env_variable "$file" "$target_go_version"
+done
+
+echo "All YAML files pass the Go version check for Go version $target_go_version."